ML19350A416

Summary of 810218 Meeting W/Anchor/Darling Industries in Bethesda,Md Re Dyna A/Damp Mechanical Snubber & in Place Surveillance Testing.Design of Snubber Meets Inservice Insp Program Requirements.Addl Info May Be Requested

ML19350A416
Person / Time
Site:	North Anna
Issue date:	02/20/1981
From:	Engle L Office of Nuclear Reactor Regulation
To:	Clark R Office of Nuclear Reactor Regulation
Shared Package
ML19350A417	List: ML19350A416 ML19350A418
References
NUDOCS 8103160115
Download: ML19350A416 (16)

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MEMORANDUM FOR:

Rchert A. Clark, Chief

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Q Operating Reactors Branch #3, DL bs FROM:

Leon B. Engle, Project Manager Operating Reactors Branch #3, DL iG

SUMMARY

OF MEETING WITH ANCHOR / DARLING INDUSTRIES INC.

FOR DISCUSSING THE dyna A/ Damp MECHANICAL SNUBBER AND IN-PLACE SURVEILLANCE TESTING A meeting was held in Bethesda, Maryland on February 18, 1981 with a representative of Anchor / Darling Industries, Inc. (A/0) and the NRC staff regarding the subject noted above. A list of attendees is provided in Attachment No. 1.

==

Introduction:==

A/D stated that it's dyna A/ Damp (dA/D) mechanical snubber is a non-locking.:

velocity limiting device, that is always engaged and responds immediately to dynamic loadings.

The dA/D mechanical snubber is unlike other mechanical snubbers since there are no complex clutches or spring mechanism used in the design of the snubber. The dA/D snubber, being all-mechanical, eliminates leaky fluids and leakprone seals and does not need lubrication or adjustment.

An oscillatory type escapement mechanism restricts pipe movement to a constant velocity for dynamic loadings; but gradual movements, such as related to temperature, are practically unrestricted. A/D further stated that the dA'P snubber is designed and manufactured to the standards specified by ASME,Section III, Subsection NF and ANSI B 31.1. Also, the dA/D snubber can be tested in-place for operability without being removed from piping or supports.

Discussion:

(1) Design:

The basis concepts used in the design of the dA/D mechanical snubber are described in Attachments No. 2 and No. 3 to this memorandum.

It should be noted that the velocity is proportional to the displacement force and is held to a maximum of.l.1 inches per second regard 1 css of load duration. The response to dynamic loadings is instantaneous and the dA/D snubber is always engaged. The compression tension characteristics are practically identical hnd the snubber has a low breakaway force. The dA/D operates over a. full-range of loads and frequencies (See Attachment No. 2).

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. (2) Static / Dynamic Testing:

The dA/D snubber has been tested for both static and dynamic lcads.

Break-away force responds to less than ? nercent of rated load. The dA/D has been tested to rated loads for more tron 15,000 cycles. The snubber has also been tested for 1.2 X 108 cycles at 20 Hz with a total displacement of 0.025 inches.

For the tests above, A/D stated no appreciable changes in drag or dynamic characteristics were noted. Upon disassembly of tested units no excessive wear or damages to integral parts was noted.

The dA/D snubbers were tested for the full range of seismic frequencies and acceleration, and velocity tests were performed over the entire stroke at full rated load without lock-up or damage.

(3) Environmental Qualification and Testing:

A/D stated that the dA/D mechanical snubber has been immersed in water, baked in ovens and exposed to saturated steam. Also the snubber has been exposed to salt spray, sand and dust with no deleterious effects noted in the mechanical snubber performance capabilities (See page 60, Attachment No. 3).

(4) In-Place Testing:

The dA/D snubbers are designed to facilitate inspection without being removed from the in-place snubber location. The inservice inspection is performed by (1) loosening the snubbers locking collar in order to allow free travel of the snubber housing (See Figure 1, Attachment No. 2), (2) a test fixture is then mounted on built-in test pins, and (3) a torque wrench can then be used to measure the force required to operate the dA/D snubber. A/D stated these measurements would normally be made on a test stand after removal of an in-place mechanical snubber with the attendant possibilities for snubber damage and increased inspection time.

==

Conclusion:==

A/D asked the NRC staff present, whether the design and specifications of the dA/D mechanical snubber was acceptable for meeting the inservice inspection program as specified in Section 4.7.9, paragraph E, sections 1, 2 and 3 of the Technical Specification Revisions for Snubber Surveillance issued November 20, 1980. The NRC staff stated that the design of dA/D mechanical snubber was applicable for meeting the inservice inspection program specified in Section 4.7.9.

However, the staff may request additional information from A/D regarding the dA/D specifications.

1

_ eon B. Eng Project Manager Operating Reac ors Branch #3, DL Att3chments:

l.

List of Attendees 2.

DYNA / DAMP Mechanical Snubber 3.

PUP-42, Component Support Snubbers-Design, Application and Testing.

cc: Se9 nest page

MEETING SUMMRY DISTRIBUTION

• Copies also sent to those people on service (cc) list for subject plant (s).

Docket File KWichman

.NRC PDR RVollmer L PDR JKnight TERA RBosnak NSIC FCherny ORB Rda FSchauer VNoonan SPawlicki HDenton RGamble ECase WHazelton DEisenhut RPurple ZRosztoczy CHofmayer RTedesco DReiff-TNovak Glainas RReid TIppolito SVarga DCrutchfield RAClark ORB Project Manager Licensing Assistant DELD AEOD - JHeltenes IE-3 SShowe (PWR) or CThayer (BWR), IE RFraley, ACRS (16)

Program Support Branch GZech J01shinski BGrimes, DEP Sheldon Schwartz, DEP FPagano^, EPLB Steve Ramos, EPDB Mtg. Summary Dist.

NRC Participants EBrown LEngle DGuzy EHemminger RKiessel HShaw l

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ATTACHMEf1T NO. 1 MEETIliG WITH ANCHOR / DARLING INDUSTRIES, IfiC.

FEBRUARY 18, 1981 i

LIST OF ATTENDEES i

NRC ANCHOR / DARLING E. J. Brown W. A. Benning L

B. Engle D..Guzy

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AlTACHMLf1T T10. 2 DYNA / DAMP MECliANICAL SNUBBER Arit lior /D.irline; Industries, Inc.

P.O. Ilox 300, Warnhold Ild.

Kulpsville, PA 19!1843

ANCilOR / DARLING INDUSTRIES, INC.

The dyna / Damp snubber is a product of Anchor / Darling Industries, Inc.

Through its subsidiaries, affiliates and licensees, Anchor / Darling has been designing and manufacturing products for the nuclear power industry since its inception.

Anchor / Darling's affiliate, Bergen-Paterson Pipesupport Company, is a leading supplier of pipe restraint systems in which the snubber is a component.

Bergen-Paterson's engineering expertise in this field provided the technical support for the development of the dyna / Damp snubber. The extensive Bergen-Paterson test facilities at Laconia, NH are utilized for qualification and other test programs to support product improvement and new product development.

dyna / Damp snubbers are manufactured in Anchor / Darling's new plant in Kulpsville, PA at the northern edge of metropolitan Philadelphia. Completed in 1980, this facility was designed specifically for the manufacture of dyna / Damp snubbers and ADAC electric actuators for valves.

The dyna / Damp snubber is the latest result of Anchor / Darling's con-tinuing search to provide better, more reliable products for electric power plant construction and operation.

4

FORWARD The Anchor / Darling mechanical snubber incorporates the principle of limiting velocity by interconnecting an oscillating type escapement (verge) with a rotating member (verge whcci) to control the rate of linear displacement of the shaft.

Linear motion of the shaft rotates the verge wheci thru step-up gearing. The verge, with predetermined engagement angles, oscillates i

when the verge wheel rotates. The relationship of the engagement angles allows the verge to reverse direction for each half tooth move-ment of the verge wheel, thus the period of oscillation controls the rate of linear movement.

During normal thermal cycles, the rack is free to displace with relatively small resistance. Upon introduction of an externally applied force - such as a seismic disturbance - oscillation of the verge creates sufficient resistance to limit movement to a constant velocity at a given load. Since the snubber is always engaged, instant snubbing action assures positive displacement control of the connected piping or equipment.

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MECHANICAL ENERGY ABSORPTION The function of the verge and verge wheel mechanism is to absorb mechanical energy.

This is accomplished by the acceleration, stop, and reverse accelera-tion of the verge mass created by the rotation of the verge wheel. The amount of energy absorbed is related to, (1) the mass, (2) the effective angles of the verge pallets, and (3) the number of circular pitch encom-pased by the verge.

The greater the circular pitch of the mechanism, the more efficient the pallet angles become and the easier the verge is oscillated, thus requiring more oscillations or an increase in mass to absorb the same energy as a mechanism with lesser spread. See sketches 1 through 3.

The design criteria for the verge and verge wheel is thus related to the amount of energy to be absorbed. In addition, the initial drag force or load required to overcome static friction must be considered.

To allow case of movement under low loads, the mechanism is designed to operate at 1-27, of rated load.

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IPTRODUCTION The design data in this bulletin applies to the Mechanical Snubber sizes listed below. Qualification tests have been conducted for the sizes listed.

The Anchor / Darling Mechanical Snubber is currently available in the following sizes:

RATED LOAD (LBS.)

STANDARD STROKE (INCHES) 400 3

700 4

1500 4

5000 5

This snubber line is offered with accessories including:

Structural Attachments Transition Kit Test-in-Place Tool I

l Noteworthy features of the Anchor Darling Mechanical Snubbers include:

Corrosion resistant No routine maintenance I

Test in place feature for field inspection t

Adjustable length on some models i

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I ECllNICAL ANNOUNCl MI NT S ubject : Anchor / Darling 1.arge Capacity Mechanical Snubber Anchor / Darling is currently designing and testing a mechanical snubber product line for load applications of 16,000 lbs. through 125,000 lbs.

These new rugged products will be of inline tubular design, constructed of corrosion resistant materials. The Anchor / Darling patented verge prin-ciple will be incorporated to provide velocity limiting characteristics. The verge mechanism is driven through a ball screw translation converter and step-up gearing.

Testing has proven that the rugged design, which incorporates

'ad a c d design concepts, produces superior dynamic characteristics, low I

vne drag, and increased cyclic life.

In addition, our units are dimensionally compatabic for use in retro-fitting existing snubber applications.

The product line will be available in early 1981.

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